Question

【題目】Directions: Fill in each blank with a proper word chosen from the box. Each word can be used only once. Note that there is one word more than you need.

To many of us, the bilateral symmetry（左右對稱） that characterizes the human face and the animal kingdom may be one of the first impressions we get of the world. If you reflect the left half of the face or body in a mirror, you obtain something that closely 【1】 the right half. Bilateral symmetry is so common that it could 【2】 be due to chance. If you think of the human body as a collection of some ten thousand trillion molecules, then there are countless ways to combine them into non-symmetrical shapes than into symmetrical ones. Why is it, then, that bilateral symmetry is so common? Given that all life on Earth slowly 【3】 through natural selection, the fact that we and many animals possess left-right symmetry, not, say, up-down or front-back symmetry, must have somehow 【4】 certain advantages. But how?

We can understand at least some parts of this natural “engineering” 【5】 by considering some simple physical principles. First, on the surface of the Earth, the Earth’s gravity introduces a 【6】 difference between up and down. Animals had to be able to remain stable and to cope with their weight under Earth’s perpetual downward pull. The ability to move further enhanced the difference between top and bottom.On one hand, birds had to handle the aerodynamics of flying, and on the other, be able to handle landing. Land animals had to develop some “mechanical” appendages (in other words, legs) to allow them to 【7】 themselves efficiently.

Animal locomotion was probably also 【8】 for the front-back asymmetry. Whether it was a bird, or a fish, having the sensory organs and the mouth in the front could mean the difference between finding lunch or missing it. The digestive and reproductive systems were pushed to the rear. Having eyes, ears, and noses in the front was also 【9】 for the avoidance of predators, and for the ability to explore an area before actually entering it. Life 【10】 that are fixed in one place or that move very slowly, such as trees or jellyfish, tend to have a different kind of symmetry, similar to that of a cone(球果) — they produce similar reflections in any mirror passing through their central axis.

Answer 1

【答案】

【1】D

【2】J

【3】C

【4】E

【5】K

【6】F

【7】B

【8】I

【9】H

【10】G

【解析】

這是一篇說明為。文章介紹了人類與動物在對稱上的區(qū)別。對大多數(shù)人來說人類面部和動物王國的對稱特征可能是我們對世界的第一印象之一。我們和許多動物都具有左右對稱的特征，而不是上下對稱或前后對稱，這一事實(shí)在某種程度上賦予了我們某些優(yōu)勢。

【1】考查一般現(xiàn)在時態(tài)。句意：如果你把臉或身體的左半邊反射到鏡子里，你就得到了與右半部分非常相似的東西。結(jié)合句意可知此處用動詞resemble“類似，想象”，再根據(jù)句子用一般現(xiàn)在時態(tài)，something是先行詞，所以謂語動詞用第三人稱單數(shù)形式，故填D。

【2】考查副詞。句意：左右對稱是如此普遍，以至于它幾乎不可能是偶然的。此處hardly“幾乎不”是副詞，修飾整個句子，符合句意。故選J。

【3】考查動詞時態(tài)。句意：既然地球上所有的生命都是通過自然選擇慢慢進(jìn)化而來的，那么我們和許多動物都具有左右對稱的特征，而不是上下對稱或前后對稱，這一事實(shí)一定在某種程度上賦予了我們某些優(yōu)勢。此處evolve“進(jìn)化”是動詞，句子用一般過去時態(tài)evolved，符合句意。故選C。

【4】考查情態(tài)動詞must have done的用法。句意：既然地球上所有的生命都是通過自然選擇慢慢進(jìn)化而來的，那么我們和許多動物都具有左右對稱的特征，而不是上下對稱或前后對稱，這一事實(shí)一定在某種程度上賦予了我們某些優(yōu)勢。此處是must have done結(jié)構(gòu)，表示對過去事情有把握的肯定推測，grant“授予”是動詞，用過去分詞的形式granted，符合句意。故選E。

【5】考查名詞。句意：通過考慮一些簡單的物理原理，我們至少可以理解這個自然“工程”之謎的某些部分。此處puzzle“謎，難題”為名詞，符合句意。故選K。

【6】考查形容詞。句意：在地球表面，地球的重力在上下之間產(chǎn)生了明顯的差異。此處是形容詞作前置定語，修飾difference。marked“明顯的”符合句意。故選F。

【7】考查動詞不定式。句意：陸地動物必須發(fā)展出一些“機(jī)械”附屬物(換句話說，腿)來讓它們有效地移動自己。固定搭配allow sb. to do sth.“允許某人做某事”。此處transport“運(yùn)輸，流放”，是動詞，作賓語補(bǔ)足語，符合句意。故選B。

【8】考查固定詞組。句意：動物的運(yùn)動也可能是造成前后不對稱的原因。固定詞組：be responsible for“對…負(fù)責(zé)”。符合句意。故選I。

【9】考查形容詞。句意：在前面有眼睛、耳朵和鼻子也是躲避捕食者的關(guān)鍵，也是在進(jìn)入一個區(qū)域之前進(jìn)行探索的能力的關(guān)鍵。此處crucial“重要的，決定性的”是形容詞，作表語，be crucial for“對…是重要的”。符合句意。故選H。

【10】考查名詞復(fù)數(shù)。句意：固定在一個地方或移動非常緩慢的生命形式，如樹木或水母，往往有一種不同的對稱性，類似于圓錐體——它們在通過其中軸的任何鏡子中產(chǎn)生類似的反射。此處form“形式”，是名詞，和life forms一起構(gòu)成句子的主語，故選G。